15% of Warming Traced to Pollutants Kyoto Doesn't Track
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- A new paper in Science finds that 15% of human-driven global warming comes from pollutants that don't directly warm the planet but trigger atmospheric reactions that generate or extend the life of greenhouse gases—with carbon monoxide and non-methane volatile organic compounds as the largest contributors, followed by black carbon.
- None of these indirect pollutants appear on the 1997 Kyoto Protocol's list of regulated gases, which the paper's authors—including a former U.S. deputy special envoy for climate and researchers from the Environmental Defense Fund—say is now a remediable gap.
- The collective impact of the indirect pollutants exceeds all but two of the seven greenhouse gases on the Kyoto list, and the study synthesized data drawn from the IPCC's Sixth Assessment Report, released in 2021.
- Unlike carbon dioxide, which persists for centuries, these pollutants are short-lived, and lead author Ilissa Ocko—a former State Department climate advisor now at Spark Climate Solutions—said cutting them could 'shave off extra fractions of a degree' of near-term warming.
- NOAA scientist Vaishali Naik, a 2021 IPCC report author, warned that 'persistent scientific and political challenges remain,' and Columbia's Michael Gerrard said 'the political climate in many countries is not for adopting even stronger climate rules.'
- The pollutants are already regulated in the U.S. and other countries as health-harming air pollutants—carbon monoxide contributes to smog—giving Ocko an opening to argue climate policy and air quality policy should not be 'siloed.'
Why it matters: Climate treaties built around the 1997 Kyoto list omit pollutants whose combined warming impact exceeds all but two of the seven gases countries actually pledge to cut. Because these pollutants are short-lived, adding them to the regulatory ledger is one of the few levers that could bend the near-term warming curve—an angle that matters most now that Ocko says 'we're already seeing damages' from current temperature levels.
